[PATCH 0/3] drm: panfrost: Coherency support

Rob Herring robh at kernel.org
Wed Sep 16 13:46:31 EDT 2020


On Wed, Sep 16, 2020 at 11:04 AM Alyssa Rosenzweig
<alyssa.rosenzweig at collabora.com> wrote:
>
> > So I get a performance regression with the dma-coherent approach, even if it's
> > clearly the cleaner.
>
> That's bizarre -- this should really be the faster of the two.

Coherency may not be free. CortexA9 had something like 4x slower
memcpy if SMP was enabled as an example. I don't know if there's
anything going on like that specifically here. If there's never any
CPU accesses mixed in with kmscube, then there would be no benefit to
coherency.

Rob



More information about the linux-amlogic mailing list